Bose Bluetooth headset microphone not working with iPhone Xs?

My old QuietComfort headphones (4 yrs old) worked great for phone calls up until about 6 months ago. Then they started dropping the microphone input (not the sound) after about 20 minutes on a phone call. I swear, this happened virtually every time and at roughly the same point in a phone call (20-30 minutes).

I ordered a new pair (same ones) from Amazon. While I got sound, the mike didn't work for phone calls. I returned those and had Amazon replace them. Second pair, exact same problem. The mike on my old pair still works fine, although it still drops the microphone reliably at 20-30 minutes into a call.

The odds against 2 bad Bose headsets in a row must be fairly high. I "troubleshot" (haha) the second pair of phones with Bose Philippine "tech support" and they could not correct the problem, either and said they would exchange them.

I sent this second pair back to Amazon and have requested a third pair. After this, I'm giving up.

Is this actually 2 bad headphones in a row from Bose or is there some hidden problem in the newer Bose/iPhone relationship???